U2 and Christina Aguilera – two of the summer’s biggest tours – have been sidelined.

U2's Bono was released from a Munich hospital Tuesday following emergency back surgery, with doctors saying the singer needed a least two months off to recuperate. That means the band’s entire North American summer tour, which was set to wind up on July 19 at New Meadowlands Stadium, has been postponed until 2011. Fans are advised to hold onto their tickets until the rescheduled dates have been set.

“Our biggest and I believe best tour has been interrupted and we’re all devastated,” U2 manager Paul McGuinnesssaid. “For a performer who lives to be on stage, this is more than a blow. He feels robbed of the chance to do what he does best and feels like he has badly let down the band and their audience – which is, of course, nonsense. His concerns about more than a million ticket buyers whose plans have been turned upside down, we all share, but the most important thing right now is that Bono make a full recovery.”

Aguilera announced Tuesday night that she was postponing her “Bionic” tour, which included a July 28 stop at Nikon at Jones Beach Theater, into 2011, citing commitments to her movie “Burlesque” and the promotion of her new “Bionic” album out on June 8. “The singer felt she needed more time to rehearse the show and with less than a month between the album release and tour date this wasn’t possible,” concert promoter Live Nation said in a statement. Refunds for that tour are available at the point of purchase.